Nitronaphthol coupler for color photography



Patented 16, 1941 NITRONAPHTHOL COUPLER FOR COLOR PHOTOGRAPHY Paul w. Vittum and Willard n. reams, Rochester,-N. Y., asslgnors to Eastman Kodak Com- Y., a corporation ofNew pauy, Rochester, N. Jersey No Drawing. Application November 17, 1939, Se-

igalehlo. 305,001. In Great Britain January 20,

12 Claims.

This invention relates to improvements in color-forming developers and particularly to processes of color development for use in connection with color photography, using novel color-forming coupler compounds.

It is known that colored photographic images may be formed by using a developer which forms a colored compound on development. The colored compound thus formed is deposited adjacent to the silver grains of the silver image during the development. It is also known that a colored image may be formed by adding to certain developer solutions or by incorporating in the gelatino-silver halide emulsion before or-aiter exposure a compoundwhich couples, during development, with the oxidation product of the developing agent and forms a coloring substance which is likewise deposited adjacent to the silver grains of the silver image during development. Such a compound, which is employed in conjunction with a developing agent for the silver 'and which couples with the oxidation product thereof during development, is referred'to herei as a color-forming coupler.

The present invention concerns new or improved color-forming' developers comprising an aromatic amino compound, serving as the developing agent. and a color coupler as hereinafter defined and also includes a new or improved color development process which consists in developing a reducible silver salt image in a photographic element with the aid of an aromatic amino compound in presence of a color-fuming coupler as hereinafter defined as well as the color photographic elements resulting therefrom. It P also includes photographic sensitive elements having such a color-forming coupler incorporated in one or more emulsion layers. g

The silver can be removed from the image after color development leaving a clear, transparent dye image.

The invention also includes a photographic element having at least one layer containing a clear, transparent image composed essentially of the product resulting from the coupling in situ, dur-,

ing development of a developable silver salt, of a color-forming coupler as hereinafter defined with the oxidation product of an aromatic amino developing agent.

When a silver halide emulsion containing a latent photographic image is developed, the silver halide is reduced to metallic silver and the de-'- veloping agent is oxidized. The aromatic diamino compounds which have been used as developing agents form, on oxidation, products which will couple with color couplers during development .to' form dyes. If such color couplers are added to the developing solution, or incorporated in the emulsion layer, the dye which is thus formed by coupling during development is deposited in the gelatine or other silver halide carrier adjacent to the metallic silver grain. It

is desirable that the dyes thus formed should not readily wander from the place of formation. It is accordingly desirable that they should be insoluble in water. They are probably not physically attached to the silver grain. The silver may be subsequently bleached out of the carrier layer leaving a pure dye image.

Numerous substances have hitherto been employed or proposed as color couplers among which maybe mentioned phenols, naphthols, cresols, nitrophenylacetonitriles and acetoacetic esters. It has not, however, always been possible among those hitherto available to select one which exhibits all the desired combination of properties required for any specific case. In color-developing a gelatino-silver-halide emulsion layer it is necessary to select a color coupler which will give just th desired shade in conjunction with the colors which are produced in otherlayers. It is moreover important to employ a color cou-- pler which gives a colored compound which is I resistant to the normal processing baths employed, although it may often be desirable to have one which gives a color which can be destroyed or removed if desired during some step in the processing.

In general, the nitro group cannot be introduced into couplers of thephenol type without reducing the coupling ability. It has been found,

however, that certain nitro derivatives of the naphthols, especially a-naphtholand its substitution products, are quitesuitable as couplers, and that many of the nitro derivatives of naph-v .thols'have distinct advantages over the corresponding compounds in which the nitro group or nitro groups is or are not present. These advantages are, in general, as follows:

(a) The dyes formed on coupling with the oxidation product of an aromatic amino developing agent have an increased absorption in the near infra-red which makes them extremely valuable for .color processes, especially three-color processes in which a sound record is to be produced in the form ofa dye image.

(b) The absorption in the visible, region is improved in that it is shifted towards the red, resulting. in improved transmission inthe green region of the spectrum. Naphthol couplers in general give dyes suitable for processing the minus-red colored image, and adequate green in the molecule.

velopers are used containing the corresponding color coupler but without th nitro group.

The presence of the nitrogroup has been found to cause no'decrease in the fastness of the resultingdyes to heat, light or moisture.

The color couplers employed according to the resent invention are suitable for use in various processes, for example. in carrying out the method described in Mannes and Godowsky U. S. Patent No. 2,113,329, granted April .5, 1938.

According. to the present invention the substance employed as a color coupler is a nitronaphth'ol, preferablya derivative of a-naphthol having one or more nitro groups. Preferably, the nitro group or nitro groups are in the ring not containing the hydroxyl group, i. e. in any of y the positions, 5, 6, 7 or 8, or in more than one 5-nitro-l-naphthol-4-sulionic acid 2,4-dibromo-5-nitro-1-naphthol of these positions. The couplers may also contain other substituents in the ring containing the hydroxyl group.

These compounds have a general structure which may be represented as follows:

where X represents a hydrogen atom or an NO: group, and one or more NO: groups are present It is to be understood that other substituents may be present, either in the ring containing the OH group or in the ring containing the N01 group or groups, as indicated by the following examples.

Examples of couplers which may be used according to the present invention are:

N O r S-nitro-l-naphthol NO: I

2,4-dichloro-5-nitro-1-naphthol 2,3,4-trichloro-5-nitro-l-naphthol The aromatic amino compounds which may be used as developing agents in the present invention include the mono-, di-, and tri-amino aryl compounds. Among themonoamino compounds maybe mentioned the aminophenols and aminocresols and their halogen substituted derivatives as well as the aminonaphthols. The developing agents usually used are the diamino compounds such as paraphenylene diamine and its substitution products. Those developers may be substituted in the amino group or in the ring or in both, forming compounds such as the alkyl phenylene diamines, toluylene diamines, alkyltoluyle'ne diamines and aminodiphenylamines. These compounds are usually kept in the salt form such as hydrochloride or sulphate since th'ese are more stable than the amines themselves. As examples of developing agents of this class, there may be mentioned diethyl para-phenylene diamine, mono-methyl paraphenylene diamine, dimethyl paraphenylene diamine and ortho-aminodiethylaniline.

As would be expected from the behaviour of known color couplers, the shade of the color obtained by coupling generally varies in accordance with the developing agent selected.

EXAMPLE A developing formula which may be used is the following:

developer or an excess, for example, 3 to 5 times such equivalent Water-miscible solvent, such as acetone cc 50 For use, B is added to A.

The developing agent and the proportions of th'e ingredients used in the above formulae may, of course, be varied. Solvents other than acetone, such as alcohols, may also be used.

The colors may, of course, be altered by inserting other substituent groups into the molecule of the coupler compounds. Y

Although we have described our invention with particular reference to the use of the color coupler in the developing solution itself, our invention is in no way limited to this method. As an alternative method, the coupler may be incorporated in the photographic layer before development; and either before or after exposure.

It may be absorbedor adsorbed to thesensitive silver halide grains.

The present invention may be utilized in the formation of colored photographic images on plates or papers as well as on films, and the dyes will be formed employing gelatin or other carrier for thesilver halide. The plates, films or papers may have difierently sensitiged emulsions of the mixed grain type or the emulsion layers may be superimposed on one side or on both sides of the support. The dyes formed may be decolorized by an oxidizing agent such as chromic acid and colorless soluble compounds thereby formed. The bleaching of the dye in this manner need not destroy the silver image but may convert it into a developable silver salt image which can in turn be colored, bleached and recolored a number of times.

It is to be understood that our invention is to be taken as limited only by the scope of the appended claims. i

What we claim and desire to be secured by Letters Patent of the United States is:

1. A color-forming photographic develope comprising. an aromatic amino developing agent and a coupler compound having the formula:

X on

comprising a dialkyl paraphenylenediamine salt and a coupler compound having the formula:

in which X is selected from the class consisting of hydrogen and nitro groups, at least one X being a nitro group. 4. A. color-formin photographic developer comprising a dialkyl paraphenyle-nediamine salt and an a-naphthol coupler compound containing at least one nitro group in the ring not containing the hydroxyl group. p

5. A color-forming photographic developer comprising an aromatic amino developing agent and a 5-nitro-a-naphthol coupler compound.

6. A color-forming photographic developer comprising an aromatic amino developing agent and 5-nitro-u-naphtho1.

7. A color-forming photographic developer" comprising an aromatic amino developing agent and a halogenated 5-nitro-a-naphthol coupler compound. I I

8. The method of producing a blue-green photographic image having high red-light absorption, which comprises exposing a gelatino-silver halide layer and treating it with a solution of anaromatic amino developing agent containing a primary amino group and an a-naphthol coupler compound containing at least one nitro group in the ring not containing the hydroxyl group, to form ablue-green dye image. 1

' green photographic images comprising a gelatine layer containing a sensitive silver halide and 9. The method of producing a blue-green-pho tographic im'age having high red-light absorption. which comprises exposing a gelatino-silver halide layer and treating'it with a solution of an aromatic amino developing agent containing a primary amino group and a 5-nitro-a-naphthol coupler compound, to form a blue-green dye image.

10. The method of producing a blue-green photographic image having high red-light absorption, which comprises exposing a gelatinosilver halide layer and treating it with a. solution of a dialkyl paraphenylenediamine salt and 5- nitro-a-naphthol, to form a blue-green. dye image.

11. A photographic emulsion for forming bluegreen photographic images comprising a carrier least one nitro group in the ring not containing 7 the hydroxyl group.

12. A photographic emulsion for forming bluea S-nitro-c-naphthol.

PAUL W. VITTUM.

WILLARD D. PETERSON. 

